1. Field of the Invention
The subject matter of the present application relates, in general, to supplying electrical loads with electrical power.
2. Description of the Related Art
FIG. 1 is a high-level block diagram of electrical power source 100 supplying three-phase electrical power to aggregate electrical loads 102, 104, and 106 (e.g., phases A, B, and C). Aggregate electrical loads 102, 104, and 106 are generally composed of several individual electrical loads. Typically, the individual electrical loads of aggregate electrical loads 102, 104, and 106 have fuses and/or circuit breakers which are constructed such that the fuses and/or circuit breakers isolate the individual electrical loads from power source 100 in the event that a short circuit to ground develops within one or more of the individual loads. As an example of the foregoing, aggregate electrical load 102 is shown composed of load_1 and load_2 which can be respectively isolated out from the phase A power line by actions of fuses and/or circuit breakers 108 and 110.
Both fuses and/or circuit breakers 108 and 110 typically require that the high current conditions responsible for either “blowing” a fuse or “tripping” a circuit breaker exist for a defined duration. The inventors have noted that when power source 100 utilizes an electronic power converter (which typically contains at least one electronic power DC/AC inverter), built-in features meant to protect power source 100 have the unexpected result of causing unnecessary “black time”—a period during which power source 100 is supplying very little effective power to aggregate loads 102, 104, and 106. For example, in many instances built-in protection features of power source 100 will interrupt the supply of power to aggregate loads 102, 104, and 106 before fuse and/or circuit breaker 108 either blows and/or trips to isolate a short circuit at load_1. Consequently, power source 100 will often “cycle” between supplying power and interrupting power since the fuse and/or circuit breaker 108 never successfully isolates short-circuited load_1.
“Traditional” power sources (e.g., AC or DC generators driven by diesel engines) employ a “short circuit ride through” technique to clear any faults within aggregate loads 102, 104, and 106, thereby shortening or eliminating “black time.” In the short circuit ride through technique, power source 100 continues to supply power to its aggregate loads 102, 104, and 106 for a period of time sufficient to clear the short circuit by blowing the fuse or tripping the circuit breaker of the shorted load. After the fault is cleared, power source 100 recovers its normal output voltage as soon as possible under the given system constraints.
The inventors have found that when power source 100 utilizes an electronic power converter, direct application of the short circuit ride through technique is not practicable. For example, when power source 100 employs an electronic power converter, the electronic power converter is typically under microprocessor control. The inventors have found that a number of reasons prevent directly implementing the short circuit ride through techniques under microprocessor control. For example, the electronic power converter often burns up or is damaged since power sources that use electronic power converters have much smaller thermal time constants than traditional power sources. In addition, the short circuit ride through techniques are inapposite to the above-discussed existing electronic converter protection routines, so it is not readily apparent how the short circuit ride through techniques may be applied when power source 100 uses an electronic power converter.
In light of the foregoing, the inventors have recognized that a need exists in the art for a process and/or device that provides the functionality of the short circuit ride through technique to power sources using electronic power converters, without damaging the electronic power converters.